Valve operation control apparatus in internal combustion engine
BACKGROUND OF THE INVENTION 
     Field of the Invention 
     This invention relates to an apparatus for control of operation of an intake or exhaust valve means in an internal combustion engine primarily for use in a vehicle. 
     The applicants in this application have disclosed in Japanese Patent Application No. 141715/Showa 56 (1981) (not prior art herein) a cylinder of an internal combustion engine with at least two intake or exhaust valves, in which either one of the two valves is provided with a pause means for stopping the opening and closing of the valve and keeping the same in its closed position so that the engine output characteristics may be improved. The pause means is operated when the engine is in its low speed range. In the apparatus the engine speed and the throttle valve open degree are detected as analog signals and the pause means is controlled in operation in accordance with a predetermined data matrix. This analog type arrangement, however, is inconvenient in that it is necessary to provide a CPU (Central Processing Unit) as a control means and consequently the apparatus is expensive. 
     SUMMARY OF THE INVENTION 
     The present invention is directed to a valve operation control apparatus for use in an internal combustion engine. The device comprises a cylinder with at least two intake or two exhaust valves, one of the two valves including a pause means for holding the valve in a closed position. The control apparatus comprises a control circuit operatively coupled to the pause means. The control circuit has at least two open degree sensors responsive to two different degrees of opening of a throttle valve of the engine and at least two engine speed sensors responsive to two different speeds of the engine, wherein the control circuit controls the operation of the pause means in response to predetermined combinations of the operation of the open degree sensors and the engine speed sensors. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a partial perspective view of one embodiment of the present invention. 
     FIG. 2 is a sectional side view of a pause means of the present invention. 
     FIG. 3 is a diagram control circuit thereof, and 
     FIG. 4 is a diagram showing engine output characteristics thereof. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring to FIG. 1, an internal combustion engine of a vehicle has a cylinder 1 with two intake valves 2 on one side thereof and two exhaust valves 3 on the other side thereof. Intake cam 4 is provided above the intake valves on the one side for driving each intake valve 2 and an exhaust cam 5 is provided above the exhaust valves 3 on the other side for driving each exhaust valve 3. 
     One of the two intake valves 2, that is, the valve 2 positioned on the upper side as viewed in FIG. 1 has a pause means 6 for stopping the opening and closing operations of the valve and keeping the valve in its closed position. Additionally, one of the two exhaust valves 3, that is, the valve 3 on the upper side in FIG. 1, has a pause means 7 for stopping the opening and closing operations of the valve and keeping the valve in its closed position. Thus, if the two pause means 6 and 7 are operated, the intake and exhaust of cylinder 1 are effected through only the intake valve 2 on the lower side and the exhaust valve 3 on the lower side as viewed in FIG. 1. 
     As shown clearly in FIG. 2, the pause means 6 comprises an electromagnetic valve 6a arranged to be closed on energization thereof. When the valve 6a is opened, a control cylinder 10 for supporting, through a spring 9, a pivot point 8a of a rocker arm 8 on the upper side of the valve 2 is opened at its outlet opening 11, and thereby pressurized oil introduced into the cylinder 10 through an inlet opening 12 is discharged through the outlet opening 11. Thus the internal pressure in the cylinder 10 is decreased and the resilient force of the spring 9 on the upper side thereof is decreased, whereby the arm 8 moves downwards at its pivot point 8a so as to be brought into its inoperative condition. In other words, when the valve 6a is opened, operation of the valve 2 on the upper side is stopped from opening and closing and is held in its closed position. This operation is similarly applicable to the pause means 7 which also comprises an electromagnetic valve 7a arranged to be closed on energization thereof. 
     According to the present invention, there is provided a control means for controlling the operations of the pause means 6 and 7. One example thereof is as shown in FIG. 3. Namely, the control means comprises a control circuit 13 with at least two open degree sensors 14 responsive to two different degrees of openings of a throttle valve of the engine and at least two engine speed sensors 15 responsive to two different speeds of revolution of the engine. 
     The at least two open degree sensors 14 comprise a sensor 14a which is a switch that closes when the throttle valve is in a full open condition which is a large open degree, a sensor 14b which is a switch that closes when the throttle valve is in a half (1/2) open condition which is a middle open degree and a sensor 14c which is a switch which closes when the throttle valve is a quarter (1/4) open which is a small open degree. The at least two speed sensors 15 comprise a sensor 15a which is a switch that closes when the engine is at a comparatively high speed N e1 , for instance, above 8000 rpm and a sensor 15b which is a switch that closes when the engine is at a comparatively low speed N e2 , that is, above 5000 rpm, for instance. The large open degree sensor 14a and the small open degree sensor 14c are connected in parallel with each other and in series with the high speed sensor 15a,  and in parallel therewith the middle open degree sensor 14b is connected to the low speed sensor 15b. The sensors are connected in a circuit with a relay 17 having a relay contact 17a connected between the electromagnetic valves 6a and 7a and an electric power source 16. 
     In operation, the output characteristics of the engine in the inoperative condition of the pause means 6 and 7 are changed in accordance with a change in throttle valve open degree, as for example shown by a curve A 1 , a curve B 1  and a curve C 1  in FIG. 4, respectively, at full open degree, 1/2 open degree and 1/4 open degree. When the pause means 6 and 7 are in their operating conditions, the characterstics are shown by a curve A 2 , a curve B 2  and a curve C 2 , respectively, in FIG. 4. 
     At the full open degree and at the 1/4 open degree, by a combination of each of the large open degree sensor 14a and the small open degree sensor 14c with the high speed sensor 15a, the pause means 6 and 7 are brought into their operative conditions in a low speed range which is below the speed N e1 . In accordance therewith the output characteristics are changed from the curves A 1  and C 1  to the curves A 2  and C 2 , respectively and consequently are improved on the lower speed side. At the 1/2 open degree, by a combination of the middle open degree sensor 14b with the low speed sensor 15b, the pause means 6 and 7 are similarly brought into their operative conditions in a low speed range which is below the speed N e2 , and in accordance therewith the output characteristics are changed from the curve B 1  to the curve B 2 , and consequently improved on the low side. Thus, at each throttle open degree, the higher characteristic is selected from the operative conditions of the pause means 6 and 7 and the inoperative conditions of the pause means 6 and 7, in relation to a change in engine speed can be obtained. 
     In the case where the open degree sensor 14 and the engine speed sensor 15 with the throttle valve being at the 1/2 open degree, for instance, are combined together as described above to obtain a higher engine output over the whole speed range, the output characteristics are increased as shown by the curve B 1  until the engine speed is decreased below the speed N e2 , and consequently this makes one&#39;s deceleration feeling unsatisfactory. For improving this unsatisfactory deceleration feeling, in the illustrated example, at least two negative pressure sensors 18 responsive to two different intake negative pressures of the engine are incorporated in the control circuit 13 so that the combinations between the open degree sensor 14 and the speed sensor 15 may be varied thereby. In the example, the above-mentioned at least two negative pressure sensors 18 comprise a sensor 18a which is a switch that closes at a comparatively high negative pressure and a sensor 18b which is a switch that closes at a comparatively low negative pressure. The sensor 18b is connected between the middle open degree sensor 14b and the low speed sensor 15b, and the sensor 18a is connected in a circuit connected between the middle open degree sensor 14b and the high speed sensor 15a. 
     With this arrangement, at the time of accelerating with the throttle valve being at the 1/2 open degree, when the middle open degree sensor 14b and the low speed sensor 15b are coupled together by closing the sensor 18b due to the increase in intake negative pressure, and the speed reaches above the speed N e2 , the characteristics are changed from the curve B 2  to the curve B 1  and consequently the feeling of acceleration is improved. On the other hand, at the time of decelerating with the same throttle valve opening condition, when the middle open degree sensor 14b and the high speed sensor 15a are coupled together by closing of the sensor 18a due to a decrease in intake negative pressure, and the speed falls below the speed N e1 , the output characteristics are changed from the curve B 1  to the curve B 2 , and consequently the feeling of deceleration is improved. 
     In the above-described arrangement, when applied to an engine for a vehicle, if the engine is revved up when the vehicle is stopped, the engine switches between its idling operation and its high speed operation, and the operations of the pause means 6 and 7 are repeated each time the engine speed is in a low speed range. This is not only wasteful but also deteriorates the durability of the means 6 and 7. For preventing this, a vehicle speed sensor 19 is provided which is responsive to a comparatively low driving speed of a vehicle, so that the pause means 6 and 7 may be held in their operating conditions by the operation of the sensor 19 without being controlled by the control circuit 13. Additionally, when the pause means 6 and 7 are an oil pressure operated type as described above, and the engine is at a comparatively low temperature, the oil for operating means 6 and 7 becomes comparatively high in viscosity, and consequently if the means 6 and 7 are repeatedly switched between operative and inoperative modes, a poor responsive property occurs and the shock on the means 6 and 7 is increased. Also the durability thereof is liable to be deteriorated. For preventing this, in the illustrated embodiment, a temperature sensor 20 responsive to a comparatively low engine temperature is provided, so that when the sensor 20 is operated, the means 6 and 7 may be held in their operating conditions, without being controlled by the control circuit 13. 
     The vehicle speed sensor 19 is a switch which is opened when the vehicle speed is below 15 km/h, for instance, and the temperature sensor 20 is a switch which is opened when the oil temperature corresponding to the engine temperature is below 40° C., for instance. The sensors 19 and 20 are connected in series to one with another, in a power circuit between the control circuit 13 and the relay 17. Thus, when the vehicle is in its stopped condition or the engine temperature is low, the means 6 and 7 are held in their operating conditions owing to cutting off of the electric current flowing to the relay 17 by the opening of the sensors 19, 20, and thereby a change between operative and inoperative conditions as described above by the control circuit 13 cannot be made. 
     Thus, according to this invention, the control circuit has at least two open degree sensors responsive to two different open degrees of a throttle valve and at least two speed sensors responsive to two different engine speeds. The control circuit controls the operation of a pause means by predetermined combinations of the open degree sensors and the speed sensors. 
     The present invention may be embodied in other specific forms without departing from the spirit or essential characteristics thereof. The presently disclosed embodiments are therefore to be considered in all respects as illustrative and not restrictive, the scope of the invention being indicated by the appended claims, rather than the foregoing description, and all changes which come within the meaning and range of equivalency of the claims are, therefore, to be embraced therein.